Reactome | 4 PBGs bind to form HMB

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4 PBGs bind to form HMB Show undefined attributes

catalystActivity	[CatalystActivity:11057271] hydroxymethylbilane synthase activity of HMBS:DIPY [cytosol]
category	transition
compartment	[Compartment:70101] cytosol
created	[InstanceEdit:11051501] Weiser, Joel, 2026-03-16
dbId	11057273
displayName	4 PBGs bind to form HMB
eventOf	[Pathway:R-SPO-189451] Heme biosynthesis - Schizosaccharomyces pombe
evidenceType	[EvidenceType:9984902] inferred by electronic annotation
followingEvent	[Reaction:R-SPO-189488] UROS transforms HMB to URO3 - Schizosaccharomyces pombe
inferredFrom	[Reaction:R-HSA-189406] 4 PBGs bind to form HMB - Homo sapiens
input	[SimpleEntity:R-ALL-29356] H2O [cytosol] 4 × [SimpleEntity:R-ALL-189464] PBG [cytosol]
isInDisease	false
isInferred	true
maxDepth	1
name	4 PBGs bind to form HMB H2O + 4 porphobilinogen => hydroxymethylbilane + 4 NH4(+) Four PBGs combine through deamination to form hydroxymethylbilane (HMB)
output	[SimpleEntity:R-ALL-189449] HMBL [cytosol] 4 × [SimpleEntity:R-ALL-31633] NH4+ [cytosol]
precedingEvent	[Reaction:R-SPO-189439] ALAD condenses 2 dALAs to form PBG - Schizosaccharomyces pombe
releaseDate	2026-03-25
schemaClass	Reaction
species	[Species:68324] Schizosaccharomyces pombe
stId	R-SPO-189406
summation	[Summation:9984901] This event has been computationally inferred from an event that has been demonstrated in another species. The inference is based on the homology mapping from PANTHER. Briefly, reactions for which all involved PhysicalEntities (in input, output and catalyst) have a mapped orthologue/paralogue (for complexes at least 75% of components must have a mapping) are inferred to the other species. High level events are also inferred for these events to allow for easier navigation. More details and caveats of the event inference in Reactome. For details on PANTHER see also: http://www.pantherdb.org/about.jsp

Referrals

(hasEvent)	[Pathway:R-SPO-189451] Heme biosynthesis
(precedingEvent)	[Reaction:R-SPO-189488] UROS transforms HMB to URO3
(inferredTo)	[Reaction:R-HSA-189406] 4 PBGs bind to form HMB

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